Defects such as Mura (uneven display brightness) that may significantly affect display effect usually are occurred during an existing manufacturing process of display device. For example, in an Active-Matrix Organic Light Emitting Diode (AMOLED) display device, several factors such as default voltage drift, aging of OLED elements and craft difference between pixels may lead to difference in brightness between pixels, resulting in dark spots, dark regions or stripes displayed in an image, which severely influences the display effect of the image.
In order to prevent display panels with such kind of failures from being manufactured into final products by normal process, flowing into the market and finally resulting in waste of both human labors and materials, samples with such kind of failures must be detected quickly and timely during the manufacturing process of the display panels. In this regard, a light-on test may be performed to detect some obvious Mura failures from appearance of the samples, which however cannot comprehensively reflect subtle differences in brightness between pixels and may easily cause missing detection. As a result, the samples with certain failures may be transferred to subsequent processes and lead to waste of both human labors and materials.